Conventionally, bases such as cemented carbide with coating layers of multiple layers such as a TiCN layer and an Al2O3 layer formed by deposition on the surfaces of the bases are widely used for cutting tools widely used for metal cutting work. In addition, it is known that the corrosion resistance of cemented carbide is enhanced by a Cr constituent contained in the cemented carbide, besides WC.
On the other hand, Patent Document 1 discloses a cutting tool coated with a TiN layer, a TiCN layer, a TiC layer, a TiCNO layer, an Al2O3 layer, and a TiN layer in order on the surface of a base by a CVD (chemical vapor deposition) method, where W and Co are diffused and contained at crystal grain boundaries of the TiN layer on the side closer to the base, the TiCN layer, and the TiC layer.
In addition, Patent Document 2 discloses a method of diffusing a Co constituent as well as a Cr constituent in a base of cemented carbide into a Ti-based coating layer on the side closer to the base, thereby enhancing the oxidation resistance of the Ti-based coating layer.